Synaptic pathways in the retina will be investigated with regard to their chemical transmitters, membrane receptors, and role in color vision and other retinal functions. Pathways will be studied morphologically by light and electron microscopy including computer-assisted three-dimensional reconstruction from serial sections. Cells which transport putative transmitters selectively, and receptor sites, will be localized by high-resolution autoradiography. Neuroactive peptides will be localized by immunocyto-chemistry. Binding sites for alpha-bungarotoxin will be localized by histochemistry for coupled horseradish peroxidase. Effects of putative synaptic transmitters on postsynaptic0cells will be analyzed by recording from single cells in the isolated superfused retina while applying those substances.